In the related art, wrist watches are exemplified as devices provided with power generation devices from among body-mounted devices (wearable devices) designed on the assumption of mounting on users. As the power generation devices provided in the wearable devices, a solar power generation device that generates power by solar light, a kinetic mechanism that uses vibration and generates power by self-winding, and a thermoelectric power generation device that generates power by a temperature difference between a body temperature and an ambient temperature, for example, are known. In addition, there is also a ring-type wearable device that uses electric power generated by using a body temperature to display letters or the like on the surface thereof. For example, Patent Literature 1 discloses a wrist watch provided with a solar power generation device. Patent Literature 2 discloses a wrist watch provided with a kinetic mechanism. Patent Literature 3 discloses a wrist watch provided with a thermoelectric power generation device.
A mobile-type electrical storage device provided with an appearance of an accessory is known though no power generation device is mounted thereon (Non-Patent Literature 1). There is also a combination-type bracelet that can be configured into a desired bracelet as an accessory by selecting arbitrary parts though the bracelet is not a wearable device (Non-Patent Literature 2).